Field of the Disclosure
This disclosure relates generally to distributed antenna systems and, more particularly, to protecting distributed antenna systems from being electrically over powered.
Technical Background
A distributed antenna system (DAS) typically includes a plurality of spaced apart antennas configured for extending radio frequency (RF) antenna coverage of an associated system. For example, a DAS may be associated with a cellular system, a “wireless fidelity” or “WiFi” system, or a wireless local area network (WLAN) by coupling the DAS to a base transceiver station (BTS) that may be in the form of a cellular base station, a WiFi base station, or a WLAN base station. As one specific example, when cellular service is not available within the interior of a building, a DAS may be installed in the interior of the building and coupled to the antenna port or ports of a cellular BTS that may be installed in the building, for providing cellular service within the interior of the building.
In active DAS networks, the DAS being coupled to a BTS typically comprises a downlink interface being used for interfacing the BTS to the DAS. The downlink interface usually includes devices such as duplexers, amplifiers and variable attenuators. A typical downlink interface can withstand power levels of only up to few watts, and the normal operation range of the downlink interface is usually below one watt (30 dBm). However, the maximum output power of a standard cellular BTS may reach twenty Watts (43 dBm) or even more. Therefore, a cellular BTS interfaced to an active DAS is typically configured to operate with low output power to match the operational range of the downlink interface, which is usually lower than one watt (30 dBm). However, due to human mistakes or technical failures, the BTS might start transmitting its maximum output power and the downlink interface may be damaged.